The present invention pertains to a technical field of a seat load measuring apparatus which is mounted beneath seat rails for guiding a seat of a vehicle, such as an automobile, to measure a load applied to the seat. Particularly, the present invention pertains to a technical field of a seat load measuring apparatus in which each seat rail is provided with a base bracket for mounting the seat rail to a base of the seat load measuring apparatus.
As a seat load measuring apparatus of this kind, there has been conventionally proposed a seat load measuring apparatus 104 for measuring a load applied to a vehicle seat 102 on which an occupant 101 is seated, the seat load measuring apparatus 104 being mounted beneath seat rails 103 for guiding the vehicle seat 102 as shown in FIGS. 10(A) through 10(C). The seat load measuring apparatus 104 comprises bases 105 each having an upward U-like cross section. The bases 105 are fixed to seat mounting portions 107 of a vehicle body via seat brackets 106 attached to the front and rear ends of the bases 105. Each seat rail 103 and each base 105 are connected to each other by pin brackets (hereinafter, sometimes referred to as “rail brackets”) 108, as connecting brackets, having a downward U-like cross section. In this case, the seat rail 103 is strongly connected to the flat tops of the pin brackets 108 and bracket pins 109 are inserted through pin holes 108a, 108b formed in the left and right side plates of the pin bracket 108 and through pin holes 105a, 105b formed in the left and right side plates of the base 105, thereby connecting the seat rail 103 to the base 105 (for example, see Japanese Patent Unexamined Publication No. 2000-258234).
On the other hand, there has been proposed another seat load measuring apparatus comprising base members each having an U-like cross section as mentioned above, however, in which each base member is arranged such that the open side thereof faces to the floor side (downwardly). Unlike the case of the base which is arranged such that the open side faces upwardly as mentioned above, this structure eliminates the necessity of a cover for closing the U-like portion of the base member (for example, see Japanese Patent Unexamined Publication No. 2002-116081).
However, since the base 105 having the upward U-like cross section disclosed in the aforementioned Japanese Patent Unexamined Publication No. 2000-258234 is arranged such that the open side of the U-like portion faces upwardly, foreign matters such as dusts and liquid easily enter into the base 105 and are thus easily deposited in the base 105. Particularly, in case that a load sensor is arranged inside the base 105 in order to efficiently utilize the inner space of the base 105, when the occupant spills liquid such as juice, there is a possibility that the liquid is poured over electrical components of the load sensor inside the base 105. As the liquid is poured over electrical components, the durability of the electrical components is marred, and reliability of the load sensor is reduced.
To prevent the durability of the electric components from being marred due to wetting by liquid, as a conceivable way, a special component such as a cover is provided to the base 105, which has the disadvantage of increasing the number of components.
Since the pin brackets 108 are components belonging to the seat load measuring apparatus 104 not belonging to the seat rails, the pin brackets 108 are set in an assembly of the seat load measuring apparatus 104. In this assembly, the pin brackets 108 and the base 105 are integrally assembled by the bracket pins 109. Therefore, it is necessary to attach the pin brackets 108 to the seat rail 103. However, the bottom of the base 105 interferes with this work and makes this work difficult. That is, the seat load measuring apparatus 104 has relatively poor workability. Holes for allowing this attaching work may be formed in the base 105. This not only requires the step of processing the base but also lowers the strength of the base 105.
Further, large load is applied to the pin bracket 108 connecting the seat rail 103 and the base 105 of the seat load measuring apparatus 104. For example, during a vehicle collision, it is required to ensure enough strength of the pin bracket 108 for bearing this large load.
However, since the connecting structure between the seat rail 103 and the base 105 of the seat load measuring apparatus 104 disclosed in the aforementioned Japanese Patent Unexamined Publication No. 2000-258234 is achieved just by inserting the bracket pins 109 through the pin holes 105a, 105b simply formed in the left and right side walls of the base 105 having an upward U-like cross section and through the pin holes 108a, 108b simply formed in the left and right side walls of the pin brackets 108 having a downward U-like cross section, there is limitation on ensuring the sufficient strength of the pin bracket 108. That is, by enlarging the dimensions (for example, thickness and length from the pin holes 108a, 108b to the peripheral ends of the pin bracket 108) of forming parts 108c, 108d of the pin holes 108a, 108b of the pin bracket 108, it is possible to ensure some strength of the pin bracket 108. The enlargement of dimensions of the forming parts 108c, 108d of the pin holes 108a, 108b of the pin bracket 108 invites the limitation on layout and thus reduces the degree of freedom of installation.
Of course, it is possible to bear the large load during a vehicle collision even with the connecting structure by the pin bracket 108 disclosed in the aforementioned Japanese Patent Unexamined Publication No. 2000-258234. However, it is desirable to further sufficiently bear the large load without inviting the limitation on layout.
On the other hand, since the base member having a downward U-like cross section disclosed in the aforementioned Japanese Patent Unexamined Publication No. 2002-116081 is arranged such that the open side faces downwardly, the necessity of the cover for closing the U-like portion of the base member can be eliminated, thus resolving the problem of increasing the number of parts of the aforementioned Japanese Patent Unexamined Publication No. 2002-116081.
However, even the seat load measuring apparatus as disclosed in the Japanese Patent Unexamined Publication No. 2002-116081 has a problem of reducing the strength of the base member because holes for allowing this attaching work may be formed in the base member like the aforementioned Japanese Patent Unexamined Publication No. 2000-258234, thus reducing the strength of the base member.
Of course, it is possible to bear the large load during a vehicle collision even with the base member disclosed in the aforementioned Japanese Patent Unexamined Publication No. 2002-116081. However, it is desirable to further sufficiently bear the large load without inviting the limitation on layout.
Thus, there is a need for a seat load measuring apparatus being capable of preventing foreign matters from being deposited in the bases and capable of further sufficiently bearing the large load during a vehicle collision, in which though load sensors are supported by bases, the durability of electronic components is improved without any special component so as to improve the reliability of the load sensors, and the increase in number of components is inhibited to increase the degree of freedom of installation without inviting the limitation on layout.